In the field of hemodialysis and other forms of blood processing, the various techniques for gaining access to the blood stream of a patient have exhibited significant, known, technical disadvantages.
In response to this, a new technology for blood access has been developed by Vasca Inc. of Topsfield, Mass., involving an implantable port chamber in the body of a patient which is used in a manner described in PCT Publications WO98/31416 and WO99/03527, as well as in other references. Specifically, an implanted port is implanted within the skin of the patient, with a preformed needle track or xe2x80x9ctractxe2x80x9d extending from the entrance of the port through the tissue and through the skin. Thus, repeated penetration of the needle or tissue xe2x80x9ctractxe2x80x9d by an access cannula can take place without cutting of tissue, since cells similar to scar tissue form around the walls of the tissue tract, providing a result similar to the tissue track passing through earlobes in the case of pierced ears.
A Vasca or other type of implanted port communicates with a body lumen, typically a vein of the patient, but desirably with a valve that normally closes the flow path between the implanted port and the vein of the patient. When access to the blood stream is desired, (or access to another body lumen), a needle penetrates the preformed tissue xe2x80x9ctractxe2x80x9d and passes into the entrance of the port, pushing open the closure valve and thus providing access to the blood stream through the port.
It has been found to be usually desirable to also provide a flush treatment of the port interior and the tissue track leading to the skin.
This is accomplished in the prior art with a thin needle, thinner than the access needle that opens the port valve to gain access for extracorporeal blood flow, so that the thin needle enters the implanted port through the preformed tissue track without pushing open the valve. Then, flushing/disinfectant solution may pass into the port through the thin needle, with the flushing solution flowing outwardly through the tissue track along the exterior of the thin needle, to provide antibacterial flushing of the implanted port and tissue track.
The tissue track is preferably formed by a sharp needle, so that, when closed and not containing a needle, it is of the cross-sectional shape of a slit, and preferably a crescent-shaped slit, and not a round hole like a pierced ear. This provides natural sealing without substantial bleeding, after the tissue track has formed its scar tissue wall, especially in the circumstance where the tissue track leads to an implanted, valved port so that little or no blood backflow occurs when needles are withdrawn from the tissue track.
It has been found to be generally desirable for the disinfection procedure using a narrow needle to be used with every procedure of access to the tissue track. Thus it is desirable for the disinfecting needle and a needle that facilitates the dilation and stretching of the tissue track for receiving of blood access needle to work together in concert.
While dull access needles have been taught for use with preformed tissue tracks, clinical experiences show to the present that only certain types of dull access needles have been able to access such tracks, which are also called xe2x80x9cbuttonholesxe2x80x9d. Needles that have too steep a bevelled tip angle, or no bevel at all with a perpendicular, flush end, generally cannot spread apart the freshly formed tissue track after a few days of nonuse, and cannot be used to gain entry unless a trocar is used in conjunction with them. However, trocars are expensive, and are difficult to place in non-gapped relation to the overlying cannula. If a gap occurs, the resulting incision can be painful when it tears tissue along the needle track. Nevertheless, the use of dull needles is highly desirable in view of laws that are going into place in the various states of the United States and perhaps elsewhere, mandating the use of either dull needles or guarded needles, to avoid accidental needle stick.
Thus, it would be desirable for a dull, safe needle to be used to pre-dilate the buttonhole so that a subsequent dull, safe, large-port access cannula, for example a dialysis flow cannula, can be inserted without a trocar. It would be beneficial if such a predilation needle can serve as a disinfecting needle as well, so that two functions may take place: a pre-dilation of the tissue track so that a blunt, larger needle can penetrate the track, and also providing of effective antimicrobial flushing for reduction of infection in the tissue track.
By this invention, such a needle or cannula, and a method of use, is provided to address the above disadvantages and technical issues.
By this invention, a cannula set has a first cannula for entry at least partially into an implantable artificial port through a preformed needle track through the skin of a patient, for fluid flow access in either direction. The implantable port has a flow conduit for connection with a body lumen such as a vein of a patient, plus a closure member (valve) for blocking flow between the port and the body lumen. This may comprise a moveable clamp which opens and closes a flexible tubing which typically is grafted at one end to a vein of a patient and which connects with the lumen of the implantable port at the other end. The closure member is normally closed by spring action or alternatively closures such as that disclosed by ports of Ensminger, Prosl and others, which closures are openable by insertion of a properly-sized and shaped cannula into the port.
The first cannula of this invention has a proximal end which maybe is connected to a hub, a proximal portion adjacent to the proximal end, and a distal portion. The distal portion of the first cannula is of insufficient size to open the closure member when inserted into the port, for example by being of insufficient length, or of insufficient outer diameter, to actuate the closure member.
The proximal portion of the first cannula may be of larger outer diameter than the distal portion, and is proportioned to dilate the tissue surrounding the preformed needle track leading to the implanted port, to facilitate subsequent advancement of a larger diameter fluid flow cannula through the needle track after withdrawing the first cannula.
Thus, the first cannula may be passed through the needle track to engage the implanted port with the distal cannula portion without causing the closure member of the port to be opened. Flushing/disinfectant solution may then be passed into the system through the first cannula, with the result that the flushing solution flows outwardly from the port through the port interior and the needle track outside of the first cannula, to provide a disinfection and flushing of both the interior of the implanted port and the needle track, for suppression of infection. Simultaneously, the proximal portion of the first cannula stretches the tissue surrounding the preformed needle track so that, upon withdrawal, it becomes a easier matter to insert a larger, second cannula through the needle track into engagement with the implanted port. This larger, second cannula is of sufficient size to cause opening of the closure member, so that the interior of the implantable port enters into fluid flow contact with the body lumen, particularly a vein of the patient. Thus, a relatively large diameter flow access path is provided through the port and the second cannula between the patient body lumen and the exterior. In the case of hemodialysis, this permits access to the venous system of the patient, so that blood can be withdrawn from the patient, passed through a blood processing apparatus such as a hemodialyzer, hemofiltration device, or the like, and then returned again to the patient, typically by means of a second implanted port and cannula system.
Preferably, especially for purposes of hemodialysis, hemofiltration, and the like, the first cannula may be at least 15 mm. in length. Also, the proximal portion of the first cannula, typically for purposes of hemodialysis or related technologies, may have an outer diameter of about 1.2 to 2.7 mm. and the distal portion may have an outer diameter of about 0.5 to 1.5 mm. The distal portion of the first cannula of this invention has preferably one half or less diameter of the specific proximal portion utilized.
Preferably for use in hemodialysis, hemofiltration, or the like the maximum diameter of the proximal portion of the first cannula is at least 70% of a minimum outer diameter of the second cannula which is for providing fluid flow through the tissue track to and from the patient.
Preferably, for hemodialysis, hemofiltration, and the like, the proximal portion of the first cannula will have a length of at least about five millimeters, which comprises at least a substantial portion of the length of the tissue track, for pre-dilation thereof preparatory to receiving the second fluid flow cannula.
As stated, the first cannula distal portion is preferably small enough to penetrate an implanted port which has a valve (closure member) so that the distal end can enter into the port without opening the valve. Typically the distal portion has a length of about 5 mm. or more, specifically a length sufficient to penetrate into the port without opening the valve as the proximal portion of the first cannula provides pre-dilation to the tissue tract. The first cannula and hub are typically connected to a syringe, or a length of tubing, connected to or carrying a source of disinfectant solution which is capable of use for flushing of the needle track and preferably the interior of the implanted port. Thus, as the pre-dilation of the needle track takes place, a flushing step may also be provided in which typically an antibacterial solution is used, flushing the interior of the port and the walls of the tissue track while the port valve is closed. Thus the connected vascular system or other body lumen of the patient is not subjected to contact with the disinfectant solution.
The first cannula may further define a frustoconical transition portion between the proximal and distal portions.
Each of the proximal and distal portions of the first cannula may typically be cylindrical or oval in cross-section, or either of them may be tapered in a typically conical shape from proximal larger ends to distal smaller ends, as may be desired.
Preferably, the distal end of the first cannula is blunt, so that it can penetrate through the tissue track without cutting tissue. Preferably, the distal end of the first cannula may be bevelled or otherwise pointed, but it remains blunt enough to be effectively incapable of cutting through intact, typical human skin at forces of less than 100 grams. As a specific test, the cannula of this invention preferably cannot penetrate a single thickness of DuPont Linear Density Polyethylene Sclairfilm of 0.004 inch (essentially 0.1 mm.) thickness at a pressure of 70 grams, as a test for preferred bluntness in accordance with this invention. Such cannulas do not generally penetrate human skin in typical circumstances where accidental needle sticks may take place.
After the flushing and pre-dilation of the needle or tissue track has taken place, the first cannula can be withdrawn, and a second cannula of greater width may be inserted into the tissue track. This cannula also is preferably blunt, and its easy entrance into the tissue track is effected by the pre-dilation which has taken place along with the antibacterial flushing provided by the first cannula. The second cannula serves as the conduit for blood flow for hemodialysis or the like, or other desired flow.
The second cannula has a relatively large inner diameter to facilitate high blood flow rates. Also, it may be desired for the second cannula to have an inward taper between its proximal end and a distal end so that the distal end is of less diameter than the proximal end, to permit easy access through the tissue track, while allowing the maximum possible blood flow rate.
Further in accordance with this invention, a method is used for providing access through the skin of the patient for communicating with a body lumen of the patient, which method comprises the following:
A first cannula having a non-cutting forward end is advanced through a pre-formed needle track (xe2x80x9cbuttonholexe2x80x9d) through the skin of a patient, without significantly cutting tissue of the patient, while dilating at least most of the needle track with the cannula to a diameter that is about 70 to 125 percent of the minimum diameter of a subsequent cannula, but preferably no more than 100 percent. The first cannula is then removed. The second, subsequent cannula is then advanced through the dilated needle track into flow communication with the patient body lumen.
While this may be accomplished by direct communication through a xe2x80x9cbuttonholexe2x80x9d into a blood vessel of the patient or other body lumen, it is preferable for the subsequent cannula to be advanced into flow communication with a body lumen by engagement with an implanted artificial port, for example an artificial port as described in the previously cited PCT publications. Preferably, the first cannula, as before, has a distal portion of less outer diameter than the first cannula proximal portion, with the proximal portion being positioned in the needle track for dilating it. The distal portion, in this position of needle track dilation, penetrates the implanted port without opening a closure valve that separates the port from the body lumen. Then, prior to removal of the first cannula, one preferably passes flushing liquid through the first cannula, most of which liquid then passes out of the patient through the needle track, providing an antibacterial flushing effect for the suppression of infection.
Following this, the first cannula can be removed, and the second cannula inserted through the needle track into engagement with the artificial port.
The closure valve of the port opens with this larger diameter fluid flow needle, to permit abundant access to blood or other body fluids for extracorporeal processing thereof, as one use of this system, although an unlimited number of other medical uses are also contemplated, such as chemotherapy and other uses where percutaneous catheters are currently used.
Preferably in the field of hemodialysis, hemofiltration, etc., the second, access cannula is of a size of at least 14 gauge at its distal tip or larger, and, as previously stated, the second access cannula is preferably tapered so that its proximal end is larger than its distal end.
It is further preferable for the tapered second access cannula to have an angle of taper that matches a taper within an access port of the implanted port so that the cannula and the tapered access port wall can form a seal which is easily made with low connection pressures, and which is also easily broken when it is desired to remove the cannula, while reliable sealing in the manner of a luer connection may be achieved.
The respective first and second cannulas and their connected sets may be packaged in a kit or kits incorporating one or both of the cannula sets in a single package, a device for infusion through the first cannula such as a syringe, disinfecting material, gauze tape, and the like.
If desired, the first cannula may be replaced by a solid trocar having a similar shape so that a forward portion having a dull point may enter the port without opening a valve while a proximal portion of increased or increasing diameter permits pre-dilation of the tissue track for subsequent reception of the second, access cannula. The second, access cannula may be threaded around the trocar as the trocar is advanced. The trocar is of course withdrawn before the system is used, for access to body fluid such as blood.